Plant-based diet and risk of osteoporosis: A systematic review and meta-analysis

Plant-based diet is growing in popularity throughout the world for various reasons, yet its effect on bone health, especially osteoporosis, remains controversial. This systematic review and meta-analysis aim to investigate the association between plant-based diet and risk of osteoporosis.

A systematic literature search of observational studies examining the relationship between plant-based diets and osteoporosis risk was performed across PubMed, Embase, Web of Science, Scopus, and ProQuest from inception to June 1, 2024. Two reviewers independently extracted data and assessed study quality using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies and the Newcastle-Ottawa Scale. To synthesize effect estimates, a random-effects meta-analysis with inverse variance weighting was applied to pool odds ratios (ORs) and 95 % confidence intervals (CIs). Subgroup analysis and meta-regression were used to explore sources of heterogeneity.

This study encompassed 20 original observational studies collectively involving 243,366 participants. Primary analysis revealed that plant-based diet was associated with the risk of osteoporosis at the lumbar spine (OR = 2.44, 95%CI = 1.12-5.33, P = 0.02; τ² = 1.94; I² = 91.7 %), compared to omnivorous diet. The association remained directionally consistent although attenuated to non-significant at the femoral neck (OR = 1.91, 95%CI = 0.68-5.42, P = 0.22; τ² = 3.28; I² = 94.9 %). Subgroup analysis revealed vegans (FN: OR = 1.79, 95%CI = 0.94-3.54, P = 0.10; LS: OR = 1.45, 95%CI = 1.00-2.12, P = 0.05) and those who followed a plant-based diet for ≥10 y (FN: OR = 1.79, 95%CI = 1.29-2.49, P < 0.01; LS: OR = 1.35, 95%CI = 0.97-1.87, P = 0.07) to exhibit a more pronounced risk of osteoporosis. Heterogeneity was primarily driven by study design.

This systematic review and meta-analysis indicate that adherence to plant-based diet may be associated with an elevated risk of osteoporosis, particularly at the lumbar spine, among individuals following a vegan diet or following a plant-based diet for ≥10 y. However, the heterogeneity observed across studies highlights the need for well-designed prospective studies in future, to clarify this relationship.